As a way of example, WO 03/087952 A1 discloses one type of conventional image forming apparatus.
This image forming apparatus disclosed in the above document is a color laser beam printer, and it is provided with a photoconductor unit, multiple developing units which execute developing procedure with respective colors, a transfer unit, and the like, and a controller which controls those elements.
Each of the multiple developing units is stopped temporarily to be opposed to a photoconductor of the photoconductor unit, and forms a toner image of each color on the photoconductor. Therefore, those multiple developing units repeat rotation and halt integrally. In this image forming apparatus, radio communication tags each having a memory are installed on the developing units respectively, so that the developing units thus rotating and the controller are allowed to exchange data via communications. In addition, wired connection is established between the controller and a radio communication module. Since the controller manages the toner amount within each developing unit, the controller communicates with the radio communication tag on each developing unit via the radio communication module, and writes the toner remaining amount data into the memory installed on the radio communication tag.
However, in the conventional image forming apparatus, if a noise is introduced in the communication data between the controller and the unit, and data amount from the unit side is increased, and thus a receive buffer of the controller has to store unexpected volume of data. Therefore, a problem of hung-up may occur.
In addition, in the conventional image forming apparatus, there is also a problem of hung-up, for example, even when the controller sends a command to the unit side, the controller is not capable of receiving a response to the command, in the case where the controller and the radio communication module are disconnected, or in the case where the radio communication module suffers a breakdown.
Furthermore, in the conventional image forming apparatus, when the controller and the radio communication module are temporarily disconnected, or when a breakdown occurs in a part of the radio communication module, an abnormal response is sent from the radio communication module to the controller, announcing the occurrence of abnormality, in the middle of sending a command from the controller to the unit side. In cases like this, the controller is capable of handling such situation by performing command retransmission or the like, i.e., retry or the like, after a lapse of predetermined period of time from the end of the command transmission.
However, in the conventional image forming apparatus, a communication available time zone is short, during when the radio communication tag installed on each of the developing units of respective colors and the radio communication module are opposed to each other. Therefore, if the controller tries to perform a retry after a lapse of predetermined period of time from the end of the command transmission, there occurs a problem that the number of retrying counts is extremely limited.